U.S. Sens. Ed Markey and Elizabeth Warren, D-Massachusetts, pushed back Thursday against language added to the Senate Republican tax plan that could open up Alaska's Arctic Refuge to oil drilling.

Markey accused Senate Republicans of trying to "ram through" the controversial provision as a rider to the GOP tax bill, noting that several lawmakers oppose drilling in the Arctic National Wildlife Refuge.

Warren, who joined her Massachusetts Senate colleague in opposing the provision, urged Americans to help Democrats fight back against the proposal.

Markey, the sponsor of a bill introduced in April to designate the Coastal Plain of the refuge as wilderness -- a move that would help protect the land from future drilling -- announced Thursday that 41 senators have since come out in support of the measure.

The senator argued that although that number of co-sponsors would have been enough to block the drilling language if the chamber were operating under regular order, he hopes such opposition "sends a strong signal ... that the provision should not have been snuck into the Republican tax bill in the first place."

"Securing the 41st cosponsor on our legislation to permanently protect the Arctic Refuge from drilling eliminates any doubt, once and for all, that the Republicans would not be able to pass their 'Big Oil Polar Payout' under regular order," he said in a statement. "This Republican drilling plan is about as far away from regular order as Alaska is from the Capitol. Republicans should stop using parliamentary tricks to attempt to ram through drilling in the Arctic Refuge as a rider on their tax scam."

Markey, who joined activists outside the U.S. Capitol in protesting the drilling language, further argued that "the only thing fuzzier than the polar bears that call the refuge home is the Republican drilling mathematics."

He called the proposal "nothing more than a big oil polar payout."

Warren, a co-sponsor of Markey's bill, meanwhile, called the drilling language included in the Senate tax plan "a shameful handout to Big Oil executives who don't like being told an area is off-limits."

"The Arctic National Wildlife Refuge is one of the last untouched wildernesses in our country. It's a beautiful landscape teeming with life and a national treasure that we have fought to protect for nearly 40 years," she wrote in a series of tweets.

"Buried deep in the GOP tax bill - buried deep so no one would notice - is a provision to allow drilling for the first time in ANWR ... The tax/ANWR vote is happening today. And it's a close fight," she continued. "Now is the time to let (Trump) and the GOP Congress know that ANWR remains off-limits."

The Arctic National Wildlife Refuge is one of the last untouched wildernesses in our country. It's a beautiful landscape teeming with life & a national treasure that we have fought to protect for nearly 40 years. #ProtectTheArctic

Buried deep in the GOP tax bill - buried deep so no one would notice - is a provision to allow drilling for the first time in ANWR. It's a shameful handout to Big Oil executives who don't like being told an area is off-limits. #ProtectTheArctic

The latest effort to allow for drilling in the Arctic Refuge appears to have been added to the tax plan, at least in part, to help win support for the bill from Alaska Republican Lisa Murkowski -- a key vote, according to the New York Times.